Various types of glare are produced by an automotive headlamp assembly. While designers of automatic headlamp assemblies have focused on the reduction of glare that blinds oncoming drivers (referred to as disability glare and discomfort glare), foreground glare continues to be a prevalent problem for automotive headlamp assemblies. Foreground glare refers to light that reflects back into the driver's eyes off of snow-covered and/or icy roads and reduces the range of visibility of the driver so that he/she cannot see the road. Foreground glare also refers to the light that reflects off of wet roads and blinds oncoming drivers.
FIG. 1 shows a front view of a typical front lamp assembly 10 that comprises a light source 14. FIG. 2 shows a cross-sectional view of front lamp assembly 10 along line A—A. As shown in FIGS. 1 and 2, a light source 14 is positioned behind a condensing lens 12. Light source 14 is positioned at a first focal point within a truncated, generally elliptical reflector. Light (shown by lines 40) is generally emitted from light source 14 so that it reflects off of reflector 16. Light that reflects off reflector 16 is generally directed through a second focal point behind lens 12 such that light from the top of the reflector strikes the bottom portion of the lens and light from the bottom of the reflector strikes the top portion of the lens. A cutoff shield 24 is located in front of the lower half of reflector 16 so that it generally prevents most light from reaching the upper half of condensing lens 12. With the cutoff shield in this blocking position, headlamp assembly 10 will produce a low beam light pattern. The “low beam” setting and/or beam pattern decreases the amount of light projected on the road in order to prevent blinding of oncoming drivers.
In the low beam setting, a large amount of light is directed through the bottom of the lens onto the road. During snow-covered and/or icy road conditions, this emitted light will reflect off the road and result in a dangerous condition where light from the lamp assembly causes foreground glare that reduce the range of visibility of the driver of the automobile. Moreover, during wet road conditions, the emitted light will reflect off the road and blind oncoming drivers. To address these foreground glare problems, designers of lamp assemblies have added a foreground shield 22 to further reduce the amount of light that is projected onto the road directly in front of the vehicle (the foreground area). As shown in FIG. 2, a foreground shield 22 is located in between the upper half of reflector 16 and condensing lens 12 in order to further reduce the light 40 emitted from front lamp assembly 10 by preventing some of the light from reaching the bottom of condensing lens 12. In this blocking position, foreground shield 22 prevents foreground glare producing light from reaching the lower portion of lens 12. This reduces the amount of light that is projected onto the road in the low beam setting and prevents foreground glare from being reflected off the road during wet, snow-covered and/or icy road conditions.
Referring back to FIG. 1, foreground shield 22 locally blocks part of the top portion of reflector 16 and does not allow any light to pass through it. While this structure reduces foreground glare, it decreases the amount of light available for the driver to see the road. In most cases, this reduction in the amount of light available to the driver is greater than is necessary and inhibits the driver's ability to see the road. Further, when the roads are dry and foreground glare is not a problem, foreground shield 22 remains in place and further hinders the driver's ability to see the road. Accordingly, it is desirable to have an adverse weather headlamp system that reduces foreground glare during wet, snow-covered and icy road conditions, while still allowing enough light to be emitted to enable a driver to fully see the road during all weather conditions.